The Solar Sunflower: a Swiss step forward in solar power efficiency

When it comes to solar energy, efficiency is a crucial criterion, as making panels more efficient means less waste, of both energy and space. There is thus a strong desire to increase the quantity of energy that a solar cell can output from a given amount of sunlight.

A full-scale prototype

Typically, a residential solar panel will transform between 11% and 15% of the sunlight into usable energy, while this proportion can be as high as 46% for the type of panels that satellites are equipped with. However, even this gold standard pales in comparison with the Swiss-made Solar Sunflower.

The solar array, built by the company Airlight Energy in collaboration with IBM Research in Zurich, reaches an incredible efficiency of 80%. It achieves this impressive feat by focusing sunlight on one point, where the concentrated energy amounts to that “of 5000 suns”, and cleverly combining the two standard outputs of solar energy, electricity and heat.

The concentration of light is made possible by a curved array of aluminum foil reflectors, all of them directing rays of sunlight to the same point. As a consequence though, the temperature is so extremely high in this spot that, if misdirected, it might melt the aluminium structure holding the solar cells. What’s more, those cells lose their efficiency when heated up.

Heat, however, is a great source of energy that ought to be captured, and IBM, inspired by a cooling system they invented for supercomputers, has come up with a nifty way to do that. In their system, water first flows through a thin layer of micro-channels placed in closed contact with the photovoltaic cell, thus capturing its heat very efficiently. Then, instead of being cooled back down and re-directed towards the cell, the heated water is used to, say, contribute to a nearby building’s heating system. It is the smart use of this collateral heat, combined with the electrical output, that is the key to the Solar Sunflower’s efficiency breakthrough.

A rendering of the Sunflower

Thus, by bringing state of the art cooling technology to the old technique of concentrating sunlight, the Solar Sunflower is able to reach unprecedented solar power efficiency. According to Airlight Energy, these aesthetic power plants will start sprouting here and there as early as 2017.